The relative extent of myocardial infarction following acute coronary artery occlusion has been shown to be dependent on available oxygen supply to the jeopardized region and the demand of that area for oxygen. Drugs that increase oxygen supply and reduce oxygen demand of the myocardium should be capable of reducing infarct size. The calcium antagonists have been shown to decrease myocardial oxygen consumption and may increase collateral flow to an area subjected to occlusion. This study seeks to demonstrate the efficacy of the calcium antagonists in several experimental models of myocardial ischemia and infarction in the anesthetized dog. Myocardial infarct size will be related to the area at risk for development of necrosis by use of fluorescein dye and nitro blue tetrazolium stain. In addition collateral blood flow to these regions will be measured by the radioactive microsphere technique. The size, shape and transmural distribution of infarction will be determined in the absence and presence of calcium antagonists in a 2 hour occlusion and reperfusion or 2 hour low flow and reperfusion model. These drugs will also be applied to a model of multivessel disease. The proposed studies should lead to some refinement and standardization of existing models as well as the development of a new model. These studies should also provide some insight into the mechanism of action of the calcium antagonists in myocardial ischemia.